Such a satellite has been known from H. Bittner et al., The Attitude Determination and Control Subsystem of the Intelsat V Spacecraft, published in Proceedings of AOCS Conference, Noordwijk, Oct. 3-6, 1977, ESA SP-128, November 1977. By means of its attitude control system, it is able to perform a great variety of maneuvers, which are necessary in the transfer orbit and the geostationary orbit, e.g., the sun acquisition, i.e., the pointing of the x axis of its system of coordinates (x, y, z), which system is fixed relative to the satellite, to the sun; the earth acquisition, i.e., the pointing of the z axis to the center of the earth; the apogee maneuver, i.e., the pointing of the z axis in the direction of the geostationary orbit in the apogee of the transfer orbit before insertion at the apogee into the final orbit; and, finally, all simple attitude control maneuvers for continuously maintaining the desired orientation, as well as all reacquisition maneuvers in the case of loss of attitude references, such as the sun and/or the earth.
The attitude control system of this prior-art satellite contains a controller for applying the actually required control laws, final control elements, namely, attitude control nozzles, for generating controlling torques around each of the three principal axes (x, y, z) of the satellite as a function of the control signals sent by the controller, as well as sun sensors, an earth sensor, and a redundantly designed, triaxially measuring set of gyroscopes for the direct measurement of the components of the rotating velocity vector of the satellite relative to the principal axes of the satellite. The sun sensors have a first field of view, which covers, on the whole, one half of the xz plane around the negative z axis and a certain width at right angles thereto, and a second field of view, which covers, on the whole, one third of the xy plane around the x axis and a certain width at right angles thereto. The earth sensor with its optical axis is oriented, as usual, in the direction of the z axis, which is to be continuously pointed toward the center of the earth in an earth-oriented orbit.
The measuring transducers used in the attitude control system include as an essential element a triaxially measuring set of gyroscopes for the direct, measuring tracking of the components of the satellite rotating velocity vector .omega.=(.omega..sub.x, .omega..sub.y, .omega..sub.z).sup.T, which are related to the system of coordinates that is fixed relative to the satellite. These measured values are needed in the prior-art satellite, because the control is designed in the prior art system correspondingly to perform the desired attitude control maneuvers. However, the use of such gyroscopes has the serious drawback that they are electromechanical components, on which very high requirements are to be imposed especially under the extreme conditions prevailing in space, and which are very trouble-prone and susceptible to wear. The redundant design, which is necessary as a result, represents a considerable cost factor. In addition, the use of sun sensors is limited in near-earth orbits due to the relatively long eclipse times (.DELTA. time during which the sun is in the earth's shadow).